Geological asset uncertainty reduction

ABSTRACT

A system and method for performing an operation at a wellbore is disclosed. A sample is obtained from a selected depth of the wellbore. A first test is performed on the sample to obtain a first estimate of mineralogy of the sample with a first degree of certainty. A second test is selected for the sample based on the first estimate of mineralogy. The second test is performed on the sample to obtain a second estimate of mineralogy having a second degree of certainty greater than the first degree of certainty. The operation is performed at the selected depth based on the second estimate of mineralogy.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent application Ser. No. 14/943,738, filed Nov. 17, 2015, the contents of which are incorporated herein by reference in their entirety.

BACKGROUND OF THE DISCLOSURE

In petroleum exploration, a borehole is drilled through an earth formation at an exploration site or drilling site using a drill string. Formation evaluation tools, conveyed into the borehole either on the drill string or separately on a wireline tool, can be used to obtain logs of the earth formation, which logs are used to determine formation lithology. However, conventional log data does not always provide a proper characterization of a shale reservoir or other subterranean formation. In order to improve the characterization, the obtained logs are calibrated with related measurements obtained from core samples and/or cuttings obtained at various locations within the borehole. Calibration measurements on the cores and/or cuttings are generally carried out in specialized laboratories that are located away from the exploration site. This calibration process therefore usually requires several weeks to complete, which can slow down or delay drilling operations until test results come in, at a considerable cost of time and money. Additionally, cores and cuttings tend to change their chemical nature during the weeks required to perform the tests, leading to inaccurate knowledge of the earth formation.

SUMMARY OF THE DISCLOSURE

In one aspect, a method of performing an operation at a wellbore includes: obtaining a sample from a selected depth of the wellbore; performing a first test on the sample to obtain a first estimate of mineralogy of the sample with a first degree of certainty; selecting a second test for the sample based on the first estimate of mineralogy; performing the second test on the sample to obtain a second estimate of mineralogy with a second degree of certainty greater than the first degree of certainty; and performing the operation at the selected depth based on the second estimate of mineralogy.

In another aspect, a system for performing an operation at a wellbore, including: a tool configured to retrieve a sample from a selected depth of the wellbore; a first device configured to perform a first test on the sample to obtain a first estimate of mineralogy of the sample with a first degree of certainty; a second device configured to perform a second test on the sample to obtain a second estimate of mineralogy with a second degree of certainty greater than the first degree of certainty; and a processor configured to: select the second device based on the first estimate, and perform the operation at the selected depth of the wellbore based on the second estimate of mineralogy.

BRIEF DESCRIPTION OF THE DRAWINGS

For detailed understanding of the present disclosure, references should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements have been given like numerals and wherein:

FIG. 1 shows an exemplary drilling system in one embodiment of the present invention;

FIG. 2 illustrates a timeline for testing procedures performed at the test station;

FIG. 3 shows a chart illustrating a preparation stage and testing stage for various samples at the test station;

FIG. 4 shows a chart detailing a decision method for selecting which tests to perform in order for an operator to make a suitable decision with regarding the drilling operation; and

FIG. 5 shows a workflow for determining a parameter of a formation sample of the borehole;

FIG. 6 shows a workflow for completing an analysis of petrophysical properties of the formation sample; and

FIG. 7 illustrates a method for identifying a false positive in mineralogy measured on a same set of formation samples; and

FIG. 8 shows a flowchart illustrating a method of determining minerology of a rock sample obtained from a depth of a wellbore in one embodiment of the present invention.

DETAILED DESCRIPTION OF THE DISCLOSURE

FIG. 1 shows an exemplary drilling system 100 in one embodiment of the present invention. The drilling system 100 is disposed at a drilling site and includes a drill string 102 that drills a borehole 104 (as referred to herein as a “wellbore”) into a formation 106. The drill string 102 extends into the borehole 104 from a surface location 108 and includes a drill bit 110 at a bottom end for drilling the borehole 104. A rotor 110 rotates the drill string 102 to drill the borehole 104. The rotor 110 may be at the surface location 108, as shown, or a downhole motor (not shown). The drill string 102 forms an annulus 105 with a wall 108 of the borehole 104.

A pump 120 is located at the surface location 108 to circulate a drilling mud 122 from a mud pit 124 into the borehole 104. The pump 120 pumps the drilling mud 122 a from mud pit 124 through a conduit 126 into the drill string 102 at the surface location 108, and the drilling mud 122 a travels downhole through an interior bore of the drill string 102 to exit the drill string 102 at the drill bit 110. The drilling mud 122 b then travels upward from the drill bit 110 through annulus 105 and out of the borehole 104 to be returned to mud pit 124 via conduit 128. The returning drilling mud 122 b can include formation fluids that enter into the borehole 104 during the drilling process as well as rock cuttings that are produced by the drill bit 110 during drilling of the borehole 104. The drilling mud 122 b and rock cuttings can be separated from each other back at the mud pit 124.

The drill string 102 includes at least one formation evaluation sensor 113 for obtaining formation parameter measurements. The sensor 113 can be a resistivity sensor, gamma ray sensors, etc. The sensor 113 can be used as the drill string progresses through the borehole in order to obtain a log of the formation parameter with depth. The drill string 102 further includes a core sample device 114 for cutting a core sample from the formation 106 at a downhole location. The core sample device 114 is located on the drill string 102, usually near the drill bit 110, and cuts into the formation 106 to obtain a core sample. The core sample can be stored in a chamber in the drill string 102 and retrieved when the drill string 102 is tripped out of the borehole 104. In another embodiment, the core sample device 114 may be part of a wireline device that is lowered into the borehole 104 after the drill string 102 has been retrieved from the borehole 104. The drill string 102 may further include a stabilizer or other device that can be used to steer the drill string. Various drilling parameters can be applied to the drill string in order to affect the drilling operation. Exemplary drilling parameters include weight-on-bit, rotations per minute, steering parameters, etc.

The drilling system 100 further includes an on-site test station 132 for performing various tests on samples that are retrieved from the borehole 104. In various embodiments, the samples can include formation fluids retrieved by the drilling mud 122 b, core cuttings retrieved by the drilling mud 122 b, and/or core sample(s) retrieved using the core sample device 114. The test station 132 performs various tests on these samples to obtain test results that can be used to enable an operator to make a decision with respect to a future process in the drilling system 100. Due to the proximity of the test station 132 to the drilling system 100 and drill string 102, an operator can select a goal or direction regarding the drilling operation, run tests that generate information applicable toward making an informed decision regarding the selected goal or direction and come to a decision regarding the goal or direction, all while the drill string remains continuously drilling, i.e., without stopping the drilling process. In one embodiment, a portion of drilling mud 122 b (as well as the geologic fluid and core cuttings) can be circulated from the mud pit 124 to the test station 132 via a transport device 134. The transport device 134 can be a pipe or conduit, a conveyor belt, an automotive vehicle, etc. After being tested at the test station 132, the drilling mud can be returned to the mud pit 124 via transport device 136.

FIG. 2 illustrates a timeline 200 for testing procedures performed at the test station 132. In general, geologic fluid samples are most readily available to the test station 132 and are often tested first. Rock fragments, such as drill cutting and wellbore cavings, require a preparation stage prior to testing and are therefore available for testing at a time later than the geological fluid. The rock fragments can be tested after, as well as concurrently with, tests performed on the geological fluids. Core samples (e.g., whole core samples, sidewall core samples) are available to the test station 132 only after the drill string 102 has been retrieved to the surface and therefore are generally tested last.

FIG. 3 shows a chart 300 illustrating a preparation stage and testing stage for various samples at the test station 132. Drilled rock cuttings and drilling fluid are received 301 from mud pit 124. Fluids are separated from the rock cuttings and sent to a gas chromatography test device 303 while the rock cuttings are sent to a preparation stage 304 which includes sampling 305, washing 307, drying 308 and grinding 309. The gas chromatography test 301 can be run continuously during the preparation stage 304 and testing stage of the rock samples and can provide measurements that can be used as input to other tests performed at the test station 132.

The rock cuttings undergo tests which can include, but are not limited to, a microscopic mineralogical test (such as a Roqscan test) 311, X-ray diffraction 313, X-ray fluorescence 315, Fourier Transform Infrared analysis 317, and pyrolysis 319, as well as other tests not shown in FIG. 2, such as core scratching, desorption testing and acoustic velocity measurements including changes in acoustic velocity. The tests are generally based on different measurement principles or physical properties of the formation. In various embodiments, the tests can include electromagnetic testing, thermal testing or testing of thermal properties, testing the formation sample through interaction with elections, testing using separation techniques, and testing using purification techniques, isotopic testing and mechanical harness testing. While all of the tests 311-319 can be available at the test station 132 an operator may only require some of these tests in order to make a decision regarding the drilling operation.

The various tests shown in FIG. 3 take certain amounts of time. Microscopic mineralogical analysis 311 takes about 30 minutes to perform. X-ray diffraction 313 takes about 10 minutes to perform. X-ray fluorescence 315 takes about 5 minutes to perform. Fourier Transform Infrared analysis 317 takes about 2 minutes to perform. Pyrolysis 319 takes about 45 minutes to perform. The order in which a selected set of these tests is performed can be selected for efficiency, in order to produce useful information for changing or affecting the drilling process within a selected time frame. Additionally, tests can be scheduled so that test results from one test can be used as input to another test.

FIG. 4 shows a chart 400 detailing a decision method for selecting which tests to perform in order for an operator to make a suitable decision with regarding the drilling operation. The chart 400 shows a first row indicating a number of goals that are pertinent to the drilling operation. Exemplary goals include: evaluating a gas potential for a formation 401, identifying a sweet spot (i.e., a hydrocarbon location) in the formation 403, determining a trajectory for geosteering 405 and designing and optimizing a frac job 407. The second row includes various issues that are to be addressed in order for a decision to be made with respect to a given goal in the first row. Exemplary issues include: determining organic matter facies, abundance and maturity 409, determining an organic matter distribution and facies recognition 411, mapping the heterogeneities of a reservoir 413, and determining rock properties 415. The third row includes various tests that can be performed to resolve the issues in the second row. Exemplary tests include: determining a total amount of organic carbon 417, performing pyrolysis 419, performing gas extraction and analysis 421, performing a chemical analysis 423, and performing clay mineral characterization 425. Arrows between boxes indicates which issues are related to which targets and which tests are used to resolve which issues. Various of these tests include performing multiple sub-tests at the test station 132. For example, a chemical analysis 423 includes performing microscopic mineralogical analysis 311 and X-ray fluorescence 315 on the sample and a clay mineral characterization includes performing microscopic mineralogical analysis 311 and X-ray diffraction 313.

Referring still to FIG. 4, an operator can determine what goals need to be decided upon and perform tests that will provide measurements that allow the operator to make an informed decision regarding the goal. For example, the operator wishes to design and optimize a frac job 407. Designing a frac job requires mapping the heterogeneities of the reservoir 413 and determining various rock properties 415. Mapping the heterogeneities of the reservoir 413 includes performing pyrolysis 419, gas extraction analysis 421, chemical analysis 423 and clay mineral characterization 425. Determining the rock properties 415 includes chemical analysis 423 and clay mineral characterization 425. It is clear that chemical analysis 423 is performed for each of mapping the heterogeneities of the reservoir 413 and determining various rock properties 415 and need be performed only once.

In one embodiment, an operator can run multiple sample tests simultaneously. In addition, the operator can run a first test on a sample to obtain a first measurement of a parameter of the sample. The operator can then run a second test on the sample or a related to obtain a second measurement of the parameter of the sample, using the first measurement from the first test as an input to the second test. Using the results from the first test as input to the second test improves an accuracy of the second measurement of the parameter produced by the second test over a measurement of the parameter than is obtained by running the second test without input. In additional embodiments, the second measurement of the parameter can be used as an input into a third test to obtain a third measurement of the parameter, whereas the accuracy of the third measurement is improved over the accuracy of the second measurement, and so on. The parameter measurements from the first test and the second test can further be integrated with formation logs in order to calibrate the formation logs, thereby generating a near real-time Mineralogical/Geochemical/Gas analysis log of an entire shale sequence of the formation 106 during the drilling operation. In another embodiment, the first measurement is of a first parameter of the formation sample and the second measurement is of a second parameter of the formation sample, and the first measurement is used to refine, correct or calibrate the second measurement of the formation sample.

The test station 132 can therefore be used to provide a reliable preliminary Formation Evaluation and/or Reservoir Characterization, enabling an operator to optimize the drilling operation (e.g. quickly identify coring point, “sweet spot” for possible frac job, smarter completion, etc.) The methods disclosed herein can be used to select appropriate intervals for hydraulic stimulation integrating LWD/wireline logs (e.g. image log, sonic log).

The test station 132 can be a portable test station that can be moved from one drilling site to another. In one embodiment, the test station 132 can be transported on a truck or other vehicle. Rock cuttings and core samples can therefore be analyzed as soon as they are retrieved from the borehole 104, rather than after being transported to a distant laboratory. In one embodiment, a single testing device can be used to perform a plurality of tests on the formation sample. The single testing device can have equipment for performing the different tests integrated into the single testing device. In another embodiment, multiple devices can be used to perform the plurality of tests. Performing tests on-site thus leads to improved test results vs. test results from distant laboratories. Additionally, the quantity and types of tests to be run at any time can be selected during the progress of the borehole drilling. The methods disclosed herein thus allow an operator to change drilling plans (geosteering, for example) or otherwise alter a drilling parameters based on the measurements provided by the test station 132, and to provide the flexibility of different drilling plans from one well to another.

FIG. 5 shows a workflow 500 for determining a parameter of a formation parameter of the borehole. In particular, the workflow 500 shows a method for determining a mineralogy 523 of a formation layer. The workflow 500 includes tests on the formation sample by performing X-ray diffraction 501, scanning electron microscopy 503, X-ray fluorescence 505 and pyrolysis 507. The X-ray diffraction 501 can provide a measurement of mineral composition 509 of a formation sample. X-ray fluorescence 505 provides an analysis of the elemental composition 513 of the sample. Pyrolysis 507 provides a measurement of an amount of inorganic carbon (mineral carbon) 517 in a formation sample. Since X-ray diffraction 501 and X-ray fluorescence 505 are generally unresponsive to inorganic carbon, the inorganic carbon measurements 515 from pyrolysis 507 can be used to correct the elemental composition 513 obtained using the X-ray fluorescence 505, thereby providing measurements that include elemental composition and inorganic carbon 519. The X-ray diffraction 501, scanning electron microscopy 503, X-ray fluorescence 505 and pyrolysis 507 can be performed as a first tier of tests on the formation sample, which may further include high resolution microscopy.

The scanning electron microscope 503 determines a distribution 513 of atoms, grain composition, grain sizes, etc., in the formation sample. The elemental composition 511 and inorganic carbon measurements 519 can be compared with the elemental composition 511 to obtain a corrected elemental composition 517 of the formation sample. The corrected elemental composition 517 can then be used to compute mineralogy 521 of the formation sample. The computed mineralogy 521 can be compared with the mineral composition 509 from the X-ray diffraction 501 in order to improve the accuracy of the computed mineralogy of the formation sample, as shown by corrected mineralogy 523.

FIG. 6 shows a workflow 600 for completing an analysis of the petrophysical properties of the formation sample. The workflow 600 can use the corrected mineralogy 523 derived from the workflow 500 of FIG. 5 in order to correct or calibrate logs of borehole parameters or to correct or calibrate petrophysical models of the formation. The corrected mineralogy 523 provides a mineral composition 607. The scanning electron microscope 601 can be used to determine various textural properties, such as porosity and pore size distribution, dispersion, mineral particle size, mineral distribution and dispersion 607. A gas adsorption device 603 provides measurements or porosity and permeability 611, which can yield information on textural properties and an amount of gas in place within the formation sample. Pyrolosis 605 measures an organic composition of the formation sample and therefore can provide a measurement of total organic carbon (TOC) 613. Fourier Transform Infrared (FTIR) testing can be performed based on results from the pyrolosis 605. The mineral composition 607, SEM measurements 609, porosity and permeability measurements 611 and total organic carbon measurements 613 can be combined to provide a display 615 of corrected mineralogy, textural properties, gas in place and total organic carbon. The display 615 can be in the form of one or more parameter logs. Other measurements not shown in FIG. 6 can also be provided at the display 615. The displayed parameters can be compared to logs of borehole parameters obtained from wellbore measurements in order to correct and/or calibrate the wellbore logs. The displayed parameters can also be input into a petrophysical model 613 to determine various parameters, such as an amount of hydrocarbon in the formation, an ease of hydrocarbon flow in the formation, an amount of fracking fluid that is needed for a frac operation, etc. In various embodiments, the gas adsorption testing can be performed on the formation sample as a second tier of testing and the FTIR testing can be performed of the formation sample as a third tier of testing. Thus a first tier of testing can include analytical techniques using X-ray diffraction, scanning electron microscopy, X-ray fluorescence and pyrolysis. A second tier of testing can include gas content analysis techniques such as gas adsorption. A third tier of testing can include analytical techniques using infrared spectroscopy (FTIR) and surface mechanical strength and/or surface hardness.

FIG. 7 illustrates a method 700 for identifying a false positive in mineralogy measured on a same set of formation samples. Panel 702 shows two mineralogy logs that are obtained using the testing methods disclosed herein. In particular, mineralogy log 702 a is obtained using scanning electron microscopy. Mineralogy log 702 b is obtained using X-ray diffraction. In panel 704, differences in the logs are noted at different zones of the borehole. In panel 706, X-ray fluorescence data log is overlapped with the mineralogy logs 702 a and 702 b. In panel 708, a false positive in the calculated log from the scanning electron microscopy has been identified due to the comparison in pane 706 and corrected using data from the mineralogy log from X-ray diffraction measurements.

FIG. 8 shows a flowchart 800 illustrating a method of determining minerology of a rock sample obtained from a depth of a wellbore in one embodiment of the present invention. The flowchart 800 includes three illustrative stages at which tests that are performed on the rock sample in order to determine the mineralogy: Fourier transform infrared spectroscopy (FTIR) stage 802, X-ray fluorescence (XRF) stage 808, X-ray diffraction (XRD) stage 810. At each stage (i.e., after a selected test has been performed), an estimate of the minerology type of the rock sample is obtained with an associated degree of certainty. The ordering of the tests can be selected so that the degree of certainty in the mineralogy of the rock sample increases with each test. In one embodiment, the order of tests can be selected so that subsequent tests reveal and identify an instance of false positives in previous tests, thereby increasing the certainty of the mineralogy type.

As shown in FIG. 8, FTIR 802 is selected in a first stage to provide a qualitative or semi-quantitative description of the rock sample. For example, for a clay sample, FTIR 802 can indicate a clay type or clay class such as illite, glauconite, smectite, etc. The clay type informs the operator or a processor of a first estimate of the elemental composition of the clay sample. However, the clay types can have compositional overlap that brings a degree of uncertainty to the determination of the clay type. This first estimate of elemental composition be tested at the second stage, in which XRF 804 provides information about the elemental composition or chemistry of the clay sample by measuring the fluorescent X-ray emitted from the clay sample when it is excited by a primary X-ray source.

XRF 804 quantifies the elements present in the clay sample, which can help to either confirm the clay type indicated from FTIR or indicate false positive results from the FTIR stage, thereby increasing the degree of certainty of the mineralogy of the clay sample. The quantity of the elements in the clay sample can also be provided to a subsequent XRD 806 test in the next testing stage, in order to have the XRD 806 testing focus on low intensity peaks of the clays indicated by XRF 804.

XRD 806 determines the crystal structure of the clay sample and chemical composition by observing a scattered intensity of an X-ray beam hitting the rock sample. The results of the XRD 806 helps to increase the certainty of the mineralogy type of the clay sample over the certainty provided from XRF 804. The estimate of mineralogy from XRD 806 can be used to determine a final clay composition 808.

It is to be understood that the specific tests in FIG. 8 and their ordering are shown only for illustrative purposes. In one embodiment, a processor or neural network receives the result from a test, its estimate of mineralogy and the degree of certainty associated with the estimate and selects a subsequent test for the sample based on the previous estimate of mineralogy, its accompanying degree of certainty and the operation under consideration. The tests that can be selected include any of the tests discussed herein.

The processor can operate an advanced data analytics tool or program for analyzing the results of each test of the formation sample after each test is performed or after a tier of tests is performed. The data analytics tool may compare test results to data libraries (both public and proprietary) includes previously-obtained regional data that provides contextual support to data for interpreting data results. The data analytics tool can provide an indication if the results of the test are inconclusive and can require that the test be performed a second time. Alternatively, the data analytics tool can indicate that the results are conclusive and recommend a subsequent test or subsequent tier of tests on the formation sample. In various embodiments, the conclusiveness or inconclusiveness of the test can be indicated by the degree of certainty provided by the test.

While the apparatus and methods disclosed herein are described is being applicable to a drilling operation, the apparatus and methods are equally applicable to operations for developing a wellbore at a wellbore development site. Developing can include drilling, completion, production, fracking, etc. and the wellbore measurements can be obtained using any tool or workstring, not just a drill string. The various measurements obtained herein can be used to alter a drilling parameter during a drilling operation, alter a step of a completion process, alter a production parameter, make a decision with regarding to a fracking operation, etc. In one embodiment, the various measurements can be used to enhance a production of fluid from a formation.

Set forth below are some embodiments of the foregoing disclosure:

Embodiment 1

A method of performing an operation at a wellbore, including: obtaining a sample from a selected depth of the wellbore; performing a first test on the sample to obtain a first estimate of mineralogy of the sample with a first degree of certainty; selecting a second test for the sample based on the first estimate of mineralogy; performing the second test on the sample to obtain a second estimate of mineralogy with a second degree of certainty greater than the first degree of certainty; and performing the operation at the selected depth based on the second estimate of mineralogy.

Embodiment 2

The method of any prior embodiment, further comprising selecting a third test for the sample based on the second estimate of mineralogy, performing the third test on the sample to obtain a third estimate of mineralogy having a third degree of certainty greater than the second degree of certainty, and performing the operation based on the third estimate of mineralogy.

Embodiment 3

The method of any prior embodiment, wherein the first test includes Fourier Transform Infrared testing, the second test includes X-ray fluorescence and the third test includes X-ray diffraction.

Embodiment 4

The method of any prior embodiment, wherein the first test is at least one of: (i) X-ray diffraction, (ii) scanning electron microscopy, (iii) X-ray fluorescence, and (iv) pyrolysis, the second test includes gas adsorption, and the third test includes Fourier Transform Infrared testing.

Embodiment 5

The method of any prior embodiment, wherein the sample is a clay sample.

Embodiment 6

The method of any prior embodiment, further comprising estimating a clay class of the clay sample from the first test and determining an elemental composition of the clay sample from the second test.

Embodiment 7

The method of any prior embodiment, wherein the sample includes at least one of: (i) a geologic fluid obtained from the borehole; (ii) core cuttings; (iii) a core sample; and (iv) well cavings.

Embodiment 8

The method of any prior embodiment, wherein the first test includes a gas analysis on the geologic fluid and the second test includes a test on one of the core cuttings, the core sample, and the well cavings.

Embodiment 9

The method of any prior embodiment, wherein the operation includes selecting the depth for a frac operation based on the second estimate of mineralogy.

Embodiment 10

The method of any prior embodiment, further comprising calibrating a log of the formation to the second estimate of mineralogy at the selected depth.

Embodiment 11

A system for performing an operation at a wellbore, including: a tool configured to retrieve a sample from a selected depth of the wellbore; a first device configured to perform a first test on the sample to obtain a first estimate of mineralogy of the sample with a first degree of certainty; a second device configured to perform a second test on the sample to obtain a second estimate of mineralogy with a second degree of certainty greater than the first degree of certainty; and a processor configured to: select the second device based on the first estimate, and perform the operation at the selected depth of the wellbore based on the second estimate of mineralogy.

Embodiment 12

The system of any prior embodiment, further comprising a third device configured to perform a third test on the sample to obtain a third estimate of mineralogy having a third degree of certainty greater than the second degree of certainty, wherein the processor selects the third device based on the second estimate of mineralogy and performs the operation based on the third estimate of mineralogy.

Embodiment 13

The system of any prior embodiment, wherein the first device performs Fourier Transform Infrared Testing, the second device performs X-ray fluorescence testing and the third device performs X-ray diffraction testing.

Embodiment 14

The system of any prior embodiment, wherein the sample is a clay sample.

Embodiment 15

The system of any prior embodiment, wherein the first device estimates a clay class of the clay sample and the second device determines an elemental composition of the clay sample.

Embodiment 16

The system of any prior embodiment, wherein the sample includes at least one of: (i) a geologic fluid obtained from the borehole; (ii) core cuttings; (iii) a core sample; and (iv) well cavings.

Embodiment 17

The system of any prior embodiment, wherein the first device performs a gas analysis on the geologic fluid and the second device performs a test on one of the core cuttings, the core sample, and the well cavings.

Embodiment 18

The system of any prior embodiment, wherein the processor is further configured to select the depth for a frac operation based on the second estimate of mineralogy.

Embodiment 19

The system of any prior embodiment, wherein the processor is further configured to calibrate a log of the formation to the second estimate of mineralogy at the selected depth.

Embodiment 20

The system of any prior embodiment, wherein the processor further operates a data analytics program that compares a test result to a data library and provides an indication of the conclusiveness of the test and recommends an action based on the conclusiveness of the test.

The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Further, it should further be noted that the terms “first,” “second,” and the like herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the particular quantity).

The teachings of the present disclosure may be used in a variety of well operations. These operations may involve using one or more treatment agents to treat a formation, the fluids resident in a formation, a wellbore, and/or equipment in the wellbore, such as production tubing. The treatment agents may be in the form of liquids, gases, solids, semi-solids, and mixtures thereof. Illustrative treatment agents include, but are not limited to, fracturing fluids, acids, steam, water, brine, anti-corrosion agents, cement, permeability modifiers, drilling muds, emulsifiers, demulsifiers, tracers, flow improvers etc. Illustrative well operations include, but are not limited to, hydraulic fracturing, stimulation, tracer injection, cleaning, acidizing, steam injection, water flooding, cementing, etc.

While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. 

What is claimed is:
 1. A method of performing an operation at a wellbore, comprising: obtaining a sample from a selected depth of the wellbore; performing a first test on the sample to obtain a first estimate of mineralogy of the sample with a first degree of certainty; selecting a second test for the sample based on the first estimate of mineralogy; performing the second test on the sample to obtain a second estimate of mineralogy with a second degree of certainty greater than the first degree of certainty; and performing the operation at the selected depth based on the second estimate of mineralogy.
 2. The method of claim 1, further comprising selecting a third test for the sample based on the second estimate of mineralogy, performing the third test on the sample to obtain a third estimate of mineralogy having a third degree of certainty greater than the second degree of certainty, and performing the operation based on the third estimate of mineralogy.
 3. The method of claim 2, wherein the first test includes Fourier Transform Infrared testing, the second test includes X-ray fluorescence and the third test includes X-ray diffraction.
 4. The method of claim 2, wherein the first test includes at least one of: (i) X-ray diffraction, (ii) scanning electron microscopy, (iii) X-ray fluorescence, and (iv) pyrolysis, the second test includes gas adsorption and the third test includes Fourier Transform Infrared testing.
 5. The method of claim 1, wherein the sample is a clay sample.
 6. The method of claim 5, further comprising estimating a clay class of the clay sample from the first test and determining an elemental composition of the clay sample from the second test.
 7. The method of claim 1, wherein the sample includes at least one of: (i) a geologic fluid obtained from the borehole; (ii) core cuttings; (iii) a core sample; and (iv) well cavings.
 8. The method of claim 7, wherein the first test includes a gas analysis on the geologic fluid and the second test includes a test on one of the core cuttings, the core sample, and the well cavings.
 9. The method of claim 1, wherein the operation includes selecting the depth for a frac operation based on the second estimate of mineralogy.
 10. The method of claim 1, further comprising calibrating a log of the formation to the second estimate of mineralogy at the selected depth.
 11. A system for performing an operation at a wellbore, comprising: a tool configured to retrieve a sample from a selected depth of the wellbore; a first device configured to perform a first test on the sample to obtain a first estimate of mineralogy of the sample with a first degree of certainty; a second device configured to perform a second test on the sample to obtain a second estimate of mineralogy with a second degree of certainty greater than the first degree of certainty; and a processor configured to: select the second device based on the first estimate, and perform the operation at the selected depth of the wellbore based on the second estimate of mineralogy.
 12. The system of claim 11, further comprising a third device configured to perform a third test on the sample to obtain a third estimate of mineralogy having a third degree of certainty greater than the second degree of certainty, wherein the processor selects the third device based on the second estimate of mineralogy and performs the operation based on the third estimate of mineralogy.
 13. The system of claim 11, wherein the first device performs Fourier Transform Infrared Testing, the second device performs X-ray fluorescence testing and the third device performs X-ray diffraction testing.
 14. The system of claim 11, wherein the sample is a clay sample.
 15. The system of claim 14, wherein the first device estimates a clay class of the clay sample and the second device determines an elemental composition of the clay sample.
 16. The system of claim 11, wherein the sample includes at least one of: (i) a geologic fluid obtained from the borehole; (ii) core cuttings; (iii) a core sample; and (iv) well cavings.
 17. The system of claim 16, wherein the first device performs a gas analysis on the geologic fluid and the second device performs a test on one of the core cuttings, the core sample, and the well cavings.
 18. The system of claim 11, wherein the processor is further configured to select the depth for a frac operation based on the second estimate of mineralogy.
 19. The system of claim 11, wherein the processor is further configured to calibrate a log of the formation to the second estimate of mineralogy at the selected depth.
 20. The system of claim 11, wherein the processor further operates a data analytics program that compares a test result to a data library and provides an indication of the conclusiveness of the test and recommends an action based on the conclusiveness of the test. 